Experimental study of ultrasound and laser triggered droplet vaporization near a wall

Vaporization of volatile perfluorocarbon (PFC) droplets by ultrasound or laser has great potential for medical applications. However, few studies are reported for the acoustic/optical droplet vaporization (ADV/ODV) near solid boundaries of tissues. In this work, the ADV and ODV are experimentally investigated using an inverted microscope and a high-speed camera. The ADV experiment is performed using a focused ultrasound transducer with a center frequency of 3 MHz, and the ODV experiment is performed using an ND:Yag pulsed laser with a wavelength of 532 nm and gold nanoparticles for laser absorption. Based on the experimental results, the phase-changing droplets are more dynamic under the ADV condition, which affects the droplets and the surrounding liquid, than under the ODV condition, which only contributes to bubble nucleation. The effects of ambient temperature and solid properties on ADV and ODV are investigated.